I think that the combination of an engine that lasts forever, that puts the mass low and is different from anything else pretty much sums up the appeal of the K bikes for people that want to show their individuality.
When I was looking for a motorcycle to take my wife on - I'm 250 and she is 135 - I was looking specifically for shaft driven.
I have never had a motorcycle that weighed more than 360 lbs wet, so I was more than happy to find a good deal on my '85 K100 because it didn't look like a cruiser, had that iconoclastic engine and just looks right.
I have 2 RD 350's that serve the wild side and around town use and I certainly didn't was a full touring rig.
I will say that until I saw a pic of mine in an ad I had no idea that BMW produced these bikes, having raised a family and forgoing motorcycles until they were on their own.
I simply did not keep up with motorcycles - I devoted my dreaming and projects to cars.
Once I saw the pic I realized that it looked a lot profile-wise like the UJM's that I prefer and are starting to appear again.
So I discovered this board and that was it - I was a goner...
As far as the gas caps go - meh...
If the don't have a lock and they really protrude I don't care for them.
I couldn't be happier.